It’s a summary of a longer article just published by Psychology Today, which you may also read (link in the Lifehacker article).

Briefly: it’s hard to motivate yourself when you are expecting boredom or other unpleasantness from the task before you. Instead, imagine the good feelings that you will have when the task is complete. Relief, pride, the joy of getting paid, a day off, whatever is your light at the end of the tunnel. Take a moment, imagine it, feel it, associate it with the task at hand. Feeling a little more motivated now?